SYMPTOMS You usually train your hamstrings hard and heavy, and there is some development happening above the back of your knees. However, your upper hamstrings are sorely lacking improvements. From the side, your legs look underdeveloped regardless of how big your quads get, and your glutes look tired and deflated.

DIAGNOSIS The solution to this problem is simple as long as your ego stays in your gym bag. You will need to make some minor adjustments to your form for hamstring curls, and you can probably use some work on your adductors. Typically, bodybuilders with weak upper-hamstring development force their hips backward toward their heels at the end of any leg-curling movement. Mechanically, this makes it impossible for the hamstrings to completely contract, robbing you of muscle-building stimulus outside of the first one-third of the movement.

TREATMENT* Reduce the weight used in all of your hamstring exercises to almost no weight at all until you master the following form.

* Start the workout with a few sets on an adductor machine. Use low weight and high reps (between 15 and 20). You will understand why this is beneficial to building thickness in your upper hams the next day when you get out of bed.

* Choose a hamstring-curl exercise. As you curl past the bottom one-third of the movement, keep your hips forward, touching the bench or pad, so that your hipbone doesn't move behind your knee.

* Visualize contracting your hamstrings like you would your biceps. Feel the peak contraction at the very top of the movement. If you are doing it right, you will feel your inner hamstrings cramp up. Your hamstrings will be screaming for mercy at the end of your first set. If they aren't, then you are using too much resistance or you are cheating by letting your hips move backward near the top of the movement.

* For any hamstring deadlift-type exercise, make sure your back is arched, shoulders are back and butt is sticking out to ensure that your hamstrings are doing the work--not your lower-back muscles. If your lower back is sore or is getting more pumped than your hamstrings, then you are doing it wrong. TRAIN YOUR CALVES WITH PHIL HEATH to prep for Friday's installment.FLEX.